Such a vehicle gauge that is known from Patent Document WO2007042322 is shown in FIG. 1, in which it is referenced 1. It includes a support plate 2 carrying light-emitting elements that are, in this example, light-emitting diodes (LEDs) 3 uniformly distributed around a central region of said support plate.
Said support plate 2 carries a light guide 4 that is circularly symmetrical in general shape and that has a plane top face 6 defined by a circular periphery so as to diffuse the light emitted by the light-emitting elements towards it top face 6, as represented diagrammatically by arrows.
The wall provided with graduations, which is not shown in FIG. 1, extends parallel to the top face 6 while being fastened directly thereto.
The assembly made up of the light-emitting elements 3 and of the light guide 4 makes it possible to back-light the graduations of the graduated wall. The graduated wall is made of a translucent material, of the Plexiglas type or of some analogous type, and its top face is painted a dark color. The graduations correspond to portions that are not painted, so as to allow the light diffused by the light guide to pass through them.
Although those graduations extend over a circular arc having a radius greater than the radius of the top face 6 of the light guide, they emit the light diffused by the light guide 4 because said light is dispersed throughout the translucent material forming the graduated wall.
Typically, the gauge has a pivotally mounted needle situated in front of the graduated wall, and having its end positioned on the graduation corresponding to the speed of the vehicle, which speed can also be read in the dark by means of the graduations being backlit.
In addition, the gauge has means for super-illuminating a portion of the graduated region, in order to indicate to the driver other speed information distinct from the information given by the pivotally mounted needle. For example, said other speed information is the value at which the cruise control is set, which value can differ from the actual speed when the cruise control has been disengaged by braking or by accelerating.
To this end, the gauge has a spot lighting member 7, including an arm mounted to pivot about the central axis AX while extending radially relative to said axis that also coincides with the pivot axis of the needle and with the axis of circular symmetry of the light guide.
More particularly, the arm 7 is carried by a tubular pivotally mounted hub 8, and it has a free end 9 extending towards the wall (not shown), while also being situated in the vicinity of the circular periphery defining the front face 4, so as to face the graduations of the graduated wall.
As can be seen in the figures, said end 9 diffuses the light referenced 11 towards the graduated wall, in a manner such as to super-illuminate a relatively spot-like region of the graduation portion. Thus, the distance between the end 9 and the axis AX corresponds to the radius of the circular arc along which the graduations are situated.
As regards the pivotally-mounted hub 8 that surrounds the pivot pin carrying the pivotally mounted needle, it may be made of an opaque material or of a transparent material for facilitating passing the light generated by the light-emitting elements towards the light guide 4, given that, by construction, said huh is interposed between the light guide and the support plate 2 carrying the light-emitting elements 3.
The needle (not shown) and the pivotally mounted lighting member are moved and their positions are servo-controlled by a motor unit 12 fastened to the back face of the support plate 2.